Hybrids Good for the Environment?

I have always wondered if Hybrids are really better for the environment. I know they save us in gas fumes from the battery pack that is in the vehicle. This saves the over all pollution in the air. The general concept is that the vehicle uses less gas by using the battery pack as energy to run the motor.
For people that don’t know what a Hybrid vehicle is - From Wikipedia, the free encyclopedia:
Hybrid electric vehicle, increasingly common automobiles which employ both a traditional internal combustion engine and an electric motor/generators for provide motive force.
I currently work for a fleet leasing company and have seen a lot of new orders come in for the Hybrids. Every ordering cycle there are new hybrids being offered by the manufacturers. There are a lot of our customers that have started adapting a hybrid only policy. They will only allow their employees to order a Hybrid vehicle for gas savings and to provide cleaner air to the environment.
I just have always wondered what happens to the vehicle when it is time to be retired and sent to the junk yard. Will the battery packs be removed and if so can they be recycled? For instance in the Ford Escape Hybrids the battery pack is in the back of the vehicle, which is considered the trunk and close to the gas tank. This has always been a mystery to me. We might not have an answer for this yet as I haven’t seen many hybrid vehicles being taken to the junkyard yet.
I wonder if it might be a revloution in the future that car dealers pushed the hybrids on consumers and in the end the effects of the battery pack are worse for the environment then just driving a vehicle that used only gasoline. If anyone can answer this quesiton for me I would greatly appreciate it.

By Aldanah Bin Muammar